The present invention relates to truck tires, preferably super single radial truck pneumatic drive tires.
Super single tires, which are wide base low aspect ratio truck tires replacing two small base tires, so-called dual mounted tires, have been used for years on trailers. Such tires are usually of size 385/65R22,5 or 385/55R22,5 and have a maximum load-carrying capacity of 4,5 metric tons.
Over the years these wide base tires appeared more and more on trucks in the steering position because they had a higher mileage.
Recently it became of interest to use also super single tires in the drive positions. Tires in the drive position have to bear part of the trailer load and must have an increased load capacity. Tire standards define a load capacity of 5,8 metric tons and a maximum speed of 110 km/h. These tires have very low aspect ratios and are usually of size 495/45R22.5. Drive tires are exposed to harsh service conditions and conventional constructions show crown area durability problems. Furthermore the pressure distribution through the elastomeric blocks in the footprint lacks the required uniformity.
GB-A-1 567 614 discloses a pneumatic tire particularly suitable for heavy vehicles. Radially outwards of the belt layers there is at least one layer comprising metallic cords parallel to one another and substantially parallel to the circumferential direction. The metallic cords have an ultimate elongation between 4 and 8%. In a preferred embodiment the layers of extensible metallic cord are formed by a single helically wound cord.
It is known from LU-A-85 964 to wind a ribbon reinforced with cords helically in at least two layers on top the belt plies of a passenger tire. The ribbon has a width comprised between 15 and 45 mm. The reinforcing cords are preferably of nylon and have a lateral density of about 30 EPI.
FR-A-2 285 255 discloses a crown reinforcing structure for pneumatic tires including a helically wound ribbon reinforced with steel cords. The ribbon has a width comprised between 5 and 50 mm and is directly wound on the carcass ply.